ABSTRACT Male smoking prevalence in Viet Nam is one of the highest in the world (45%), and smoking rates are even higher among people living with HIV/AIDS (PLWH) (59%). PLWH who smoke are at increased risk of excess morbidity and premature death compared with nonsmokers. Yet, in Viet Nam treatment is not integrated as a routine part of care in outpatient HIV clinics (OPCs). Our long-term goal is to develop a scalable model for implementing evidence-based tobacco use treatment (TUT) in health care settings treating PLWH in LMICs like Viet Nam. The objective of this study is to conduct a 3-arm randomized controlled trial (RCT) that compares the cost-effectiveness of three multi-component interventions that are embedded in OPCs: 1) 3As+R (Standard Care (SC)): Ask about tobacco use, Advise to quit, Assist (brief counseling), and Refer to Viet Nam?s national Quitline; 2) SC+Counsel (Counsel=6-session cessation counseling intervention adapted for PLWH and delivered by a trained, onsite clinic staff; and 3) SC+Counsel+N (N=nicotine replacement therapy (NRT)). The primary outcome of this type 1 hybrid implementation trial is the effectiveness of the intervention (6-month tobacco abstinence) and secondary outcomes are measures of contextual factors that may influence implementation and sustainability. Patients (n=672) will be recruited from 14 OPCs in two cities in Viet Nam and randomized into one of 3 study arms. The proposal builds on findings from the team?s 2-arm NCI-funded cluster RCT (VQUIT) that compared two implementation strategies for increasing adoption of TUT guidelines in 26 health centers that provide primary care for a general population in Viet Nam. In VQUIT, which was implemented prior to the availability of the Quitline, clinicians in the intervention sites referred tobacco users to a trained village health worker (VHW) for 3-session cessation counseling. Control sites included a 3As only model and no referral option. Patients receiving VHW-delivered counseling plus clinician-delivered cessation advise and counseling (3As+R) had higher biochemically validated 6-month quit rates compared with those who received 3As only (25.7% vs.10.5%; p<.001). This proposal builds logically on this prior work. We will conduct formative research to further adapt and tailor the VQUIT materials to the sociocultural context of PLWH and to the HIV clinical context. We will then compare the 3As+R model (Standard care (SC) now with Quitline referral) to two enhanced models of TUT that offer: a) more intensive counseling adapted for PLWH and delivered by HIV clinicians (SC+Counsel), and b) dispensing of NRT (SC+Counsel+N). The specific aims are to: 1) Adapt and tailor the intervention to PLWH and HIV care settings, 2) Conduct a 3-arm RCT comparing the cost effectiveness of three models of care based on biochemically validated 6-month smoking abstinence; and 3) Evaluate multilevel factors that facilitate or impede implementation and potential for sustainability of TUT in HIV treatment settings in Viet Nam.